Preparation of Co–Sn alloys by electroreduction of Co(II) and Sn(II) in molten LiCl–KCl

Co–Sn alloys were prepared by an electrochemical route in molten LiCl–KCl between 400 and 550 °C. The Sn(IV)/Sn(II), Sn(II)/Sn(0) and Co(II)/Co(0) redox couples were studied by cyclic voltammetry and/or chronopotentiometry over the temperature range. The diffusion coefficient values of Co(II) ions were measured. For example, it was found that the DCo(II) values deduced from chronopotentiometry range from DCo(II) = 1.65 × 10−5 cm2 s−1 at 400 °C to 4.95 × 10−5 cm2 s−1 at 550 °C. The standard potential of the Co(II)/Co(0) redox couple in molten LiCl–KCl was measured at 400 °C: ECo(II)/Co(0)0=−1.35 V vs Cl2/Cl−. Finally, Co–Sn alloys were prepared in potentiostatic mode. The influence of the temperature of molten LiCl–KCl, the applied potential and the deposition time on the morphology and the composition of the Co–Sn alloys were also investigated. For T > 450 °C, the following tendency has been observed: the more negative the potential, the higher the Sn content in the deposited alloy. Thus, depending on the operating conditions, pure CoSn or CoSn2 can be prepared.